This invention relates generally to a sealed edge joint between two metal panels, for example, an edge joint between outer and inner panels of a vehicle closure panel assembly.
At the present time, a sealed joint between outer and inner panels of a vehicle closure panel assembly is provided by an organic-based vinyl plastisol sealant. The sealant is applied over the hem flange of the closure panel assembly typically after the first paint primer application and prior to application of a color coat to the closure panel assembly. The sealant is cured during the subsequent paint bake. The sealant is typically applied manually and is intended to resist corrosion by blocking electrolytes from entering the hem flange fold.
This edge seal has several disadvantages. If a manual application is performed, the sealant is not always uniformly applied to all areas requiring protection and it is often difficult to reach all areas of the closure panel assembly requiring protection. An automated application requires expensive capital equipment. The sealant adds little or no strength to the final panel assembly and does not provide sacrificial corrosion protection.
A sealed joint at the hem flange of a vehicle closure panel assembly has also been formed by a heat-curable resin coating as disclosed in U.S. Pat. No. 6,000,118. The closure is painted after the joint is sealed, and the coating is cured as part of the painting and baking of the paint.
In accordance with the present invention, a metal coating is provided to seal the edge of the hem flange. Preferably the metal coating is zinc or a zinc/ceramic alloy. The metal coating is mechanically sprayed on by a jet stream of metal particles.
The sprayed metal coating acts as a physical barrier or seal to prevent the entry into the hem fold of corrosion electrolytes (for example, water, salt, etc.) and also may offer sacrificial protection against corrosion. The sprayed metal coating has also been found to be compatible with downstream automotive assembly processes, including painting of the panel assembly. The sprayed metal coating can be subsequently painted over and will adhere to the paint and to the panels upon which it is sprayed.
The metal coating can be sprayed to different film thicknesses to accommodate variations in the hem tightness and panel thickness. The sprayed metal coating resists relative shifting between the door panel parts because it sets up immediately upon being sprayed on and forms a metallurgical and/or mechanical bond, thereby eliminating the necessity for welding processes and other techniques for stabilizing panel geometry. The metal coating can also be applied thinner than a vinyl sealant, minimizing the likelihood of interference between an opening for a closure panel and weather stripping.
One object of this invention is to provide a sealed edge joint for two metal panels, having the foregoing features and capabilities.
Another object is to provide a sprayed-on metal coating which seals and forms a mechanical and metallurgical bond.
Another object is to provide a sealed edge joint having a metal coating preferably made of zinc or zinc/ceramic alloy which provides sacrificial corrosion protection for closure panels constructed of steel.
Another object is to provide a method of making a sealed edge joint for two metal panels.
These and other objects, features and advantages of the invention will become more apparent as the following description proceeds, especially when considered with the accompanying claims and drawings.